A cast mould for the purpose of manufacturing contact lenses or intraocular lenses is described in, for instance, NL1033905C, EP-A-0 367 513 or in US 2009/0166507 A1. The cast mould known from NL1033905C is provided with a first cast mould half comprising an optically accurately defined surface and first positioning means. The known cast mould is further provided with a second cast mould half comprising a central part with optically accurately defined surface, a bearing ring that surrounds the central part and is provided with second positioning means which are designed for engagement of the first positioning means in a closed position of the cast mould in which the first and the second cast mould halves are placed on top of each other. For the purpose of manufacturing a contact lens or intraocular lens, a monomer material is introduced into one of the two cast mould halves and then the second cast mould half is placed on the first cast mould half. Subsequently, the monomer material will polymerize.
In NL1033905C, it is described that the positioning means can be designed for fastening the second cast mould half onto the first cast mould half and for keeping these in use on top of one another under a bias.
From NL1033905C and EP-A-0 367513 it is also known to use one of the mould halves as part of a package with which the lens can then be put on the market.
With regard to the manner of manufacture of plastic cast moulds nothing of relevance is disclosed in the publications mentioned. In this respect, more can be learned from U.S. Pat. No. 5,540,410. In particular FIG. 5 from this publication with the associated description in column 10, line 38-column 14, line 3 is especially clarifying and is therefore understood to be incorporated herein by reference. US 2006/145370 too discloses a method and an injection mould for injection moulding a cast mould. The injection mould is provided with optical tool inserts which are detachably attached in an element that is attached in the injection mould half. FR-1.355.774 describes in general terms the problem of the formation of bubbles and shrinkage cavities when the injected plastic cures in an injection mould. The French publication also describes how this shrinkage can be compensated for by using a mechanically or hydraulically energized piston which is pressed into the injection mould cavity during curing.